/Engine/Source/Runtime/Experimental/Iris/Core/Public/Iris/ReplicationState/Private/IrisFastArraySerializerInternal.h
Edit Item in array and call MarkItemDirty
[FastArrayItemType](API\Runtime\IrisCore\Iris\ReplicationState\Private\TIrisFastArrayEditor\FastArrayItemTyp-) & Edit ( int32 ItemIdx )